Structural steel is commonly used to erect a wide range of architectural structures ranging from industrial buildings to industrial process platforms. Historically these structures have been built by hoisting individual beams into position one-at-a-time and thereafter cutting, fitting and securing them into permanent position.
Over the years, there have been numerous attempts to simplify the construction procedure utilizing techniques which allow more prefabrication and fitting together of the various structural steel members and floor sections at ground level.
Exemplary prior art patents addressing such simplified construction techniques are U.S. Pat. Nos. 4,330,970 to Bonink; 3,827,203 to Berrie; 3,378,971 to Singer et al.; 2,046,152 to Dean; 3,429,092 to Perry et al., 4,640,070 to Moffat; 3,788,024 to DeHartog; 3,942,297 to Kitagawa; and 4,965,974 to Lebow.
Most of the foregoing patents disclose columnar members having some type of mating joint member in a floor or roof member of a building such that a floor section can be lowered into position over an existing array of columns so that the columns will in one way or another interlock with the floor when the means utilized to lift the floor section into place releases the tension used for lifting.
In the case of U.S. Pat. No. 3,378,971 to Singer et al., the opposed ends of the columns are tapered, and each floor section includes a mating spigot on its uppermost and lowermost surfaces to effect a joint between the floor section and each column.
In the case of U.S. Pat. No. 4,965,974 to Lebow, the columns are provided with a horizontally extending plate at each end. The lowermost base plate is provided with one or more apertures, while the uppermost capital plate is provided with at least one upwardly extending pin. The pins and the apertures are laterally spaced from the column member and are positioned to be in register with a mating aperture or pin in a floor section or frame. Each floor section or frame has a top and bottom erection plate secured at its corners. The bottom erection plate has an aperture spaced from the frame members for receiving the pin from a capital plate of a column immediately therebeneath. The top erection plate has an upwardly projecting pin, which is received in registry by the aperture on a base plate of a column in the story or level immediately above it. Thus the structure disclosed by Lebow is assembled by positioning a first group of columns with a crane and thereafter lowering a prefabricated frame or floor into position on the tops of the first group of columns. Additional stories are added by successively positioning tiers of columns and frames or floor sections in like manner.
While systems of the type disclosed in the foregoing prior art patents have met with some degree of success, there has been a growing trend toward modular construction wherein entire modules, i.e., frames or floor sections with vertical columns rigidly secured thereto, are assembled at ground level and thereafter lifted into place as a unit. This is typically accomplished by extending the length of the vertical columns slightly below the frame or floor sections during the ground level prefabrication stage and thereafter securing the bottom ends of the columns on the particular module being lifted into position to the tops of the columns on the preexisting modular section which has been installed immediately below.
Columns employing tapered ends of the type disclosed by Singer et al. in U.S. Pat. No. 3,378,971 would not be particularly well suited for this purpose because they would require the use of a specially designed female connector which would secure two opposed tapered column ends to one another, but which would not weaken the resulting columnar structure. In addition, the use of such specially designed female connectors would make it more difficult to reliably and permanently secure the load carrying vertical columns to one another.
While horizontal plates employing transversely spaced mating pins and apertures such as those disclosed in U.S. Pat. No. 4,965,974 to Lebow have been utilized to secure a joint between the bottom of the columns on the module being installed and the top of the columns on the previously installed module located immediately below, the addition of these horizontally extending plates involves the addition of a considerable amount of steel. This additional steel is not necessary from a strength standpoint in the final structure and serves no purpose other than to aid alignment of the columns of each of the modules with one another during the assembly operation. It tends to therefore increase the cost of the resulting structure. In addition, the horizontally extending plates which are necessary in order for the mating pins and holes to be laterally offset from the columns tend to cause obstructions in the resulting building structure, particularly in the areas immediately adjacent the vertical columns. This in turn makes installation of final walls, routing of pipes, routing of conduits and the like in close proximity to the vertically extending columns employing joints of this type more difficult.